P0401
TECHNICAL DESCRIPTION- When the EGR solenoid switches from "OFF" to "ON" while the engine is running, EGR gas flows.
- The ECM
DTC SET CONDITIONS
Check Conditions
- At least 20 seconds have passed since the last monitor was complete.
- Engine coolant temperature is higher than 76 °C (169 °F).
- Engine speed is at between 1,000 and 1,800
- Intake air temperature is higher than 0 °C (32° F).
- Barometric pressure is higher than 76 kPa (11 psi).
- Vehicle speed is 1.5 km/h (0.9 mph)
- At least 90 seconds have passed since manifold differential pressure sensor output voltage fluctuated 1.5 volts or more.
- The throttle valve is closed.
- Volumetric efficiency is lower than 15
- While fuel is being shut off.
- 20 seconds have elapsed from the start of the previous monitoring.
- Monitoring time: 2 seconds x 3 times.
Judgement Criteria
- The intake manifold pressure fluctuation width is lower than 3.5 kPa (0.50 psi). When the EGR solenoid is turned ON.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- EGR valve does not open.
- EGR control vacuum is too low.
- EGR solenoid failed.
- Open or shorted EGR solenoid circuit, or loose connector.
- Manifold differential pressure sensor failed.
- ECM failed.
- PCM failed.
DIAGNOSIS
Required Special Tools
- MB991502: Scan Tool (MUT-II)
STEP 1. Check the EGR system.
Refer to Emission Control System - Exhaust Gas Recirculation (EGR) System - EGR System Check.
Q: Are there any abnormalities?
YES: Go to Step 2.
NO: Repair it. Then go to Step 3.
STEP 2. Using scan tool MB991502, check data list item 95: Manifold Differential Pressure Sensor.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 95, Manifold Differential Pressure Sensor.
4. Warm up the engine to normal operating temperature: 80 °C to 96 °C (176 °F to 205 °F).
- Should be between 65 - 78 kPa at engine idling.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: Clean the EGR valve and EGR passage. Then go to Step 3.
NO: Refer to, DTC P1400 - Manifold Differential Pressure Sensor Circuit Malfunction.
STEP 3. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to, Procedure 5 - Exhaust Gas Recirculation (EGR) System Monitor.
2. Check the diagnostic trouble code (DTC).
Q: Is the DTC P0401 output?
YES: Retry the troubleshooting.
NO: The inspection is complete.